Section bars rolled in a rolling mill ordinarily have a length of several tens to several hundreds of meters. The products having been rolled are divided into products having a suitable length in accordance with the length of a cooling bed so as to be supplied to a next cooling process and cooled. The divided products having been cooled are cut and corrected again sometimes offline. Dominant in modern rolling mills, however, is a method of straightening the cooled products inline downstream of the cooling process and cutting them to a product length.
FIG. 36 is a view explaining the outline of an ordinary inline straightening/traveling cutting system in a section bar rolling line. In FIG. 36, numeral 51 denotes a multiple section bars straightening apparatus disposed to the outlet side of a cooling bed, numeral 52 denoted an inter-machine table, numeral 53 denotes a first measuring roll disposed downstream of the multiple section bars straightening apparatus 51, and numeral 54 denotes a presser roller 54 disposed downstream of the first measuring roll 53 for pressing a section bar coming off the multiple section bars straightening apparatus 51 against the inter-machine table 52.
Numeral 55 denotes a traveling cutting machine disposed downstream of the presser roller 54 and numeral 56 denotes a second measuring roll 56 disposed downstream of the traveling cutting machine 55. Numeral 57 denotes an outlet side presser roller 57 disposed downstream of the second measuring roll 56 and numeral 58 denotes a rear surface tilting table 58 disposed downstream of the outlet side presser roller 57.
Further, (a), (b) and (c) in FIG. 36 time-sequentially show the tail end of a section bar to be corrected and cut, wherein (a) shows (n-2) cut which is 2 cuts before final cut (n cut), (b) shows (n-1) cut which is 1 cut before the final cut (n cut) and (c) shows the final cut (n cut), respectively. Note that a product length is shown by L and a tail end block length is shown by 1c.
Next, a cutting job for the tail end portion of a section bar will be described based on FIG. 36.
In the state of the (n-2) cut shown in (a), the section bar is restricted by the multiple section bars straightening apparatus 51 and fed downstream, cut to the product length L by the traveling cutting machine 55 and the length of the remaining portion thereof is made to 2L+lc. Note that, the rear surface tilting table is tilted in a cutting direction so that the section bar is not bent while it is cut.
In the state of (n-1) cut shown in (b), the section bar is still restricted by the multiple section bars straightening apparatus 51 and the length of the remaining portion after it is cut by the traveling cutting machine 55 is made to L+lc.
Thereafter, since the tail end of the section bar comes off the multiple section bars straightening apparatus 51 before it is subjected to n cut, first, the section bar is fed downstream while being synchronized with the multiple section bars straightening apparatus 51 in the state that it is pressed against the inter-machine table 52 by the presser roller 54 before it comes off the multiple section bars straightening apparatus 51. After the section bar comes off the multiple section bars straightening apparatus 51, it is fed downstream by the restricting force of only the inlet side presser roller 54.
Then, as soon as the leading edge of a finally cut product (length: L+lc) is fed up to the position of the outlet side presser roller 57, it is pressed against the rear surface tilting table 58 by the outlet side presser roller 57 and subjected to the final n cut.
A reason why the section bar is restricted by the inlet side presser roller 54 and the outlet side presser roller 57 will be described.
The section bar having come off the multiple section bars straightening apparatus 51 is disposed such that it can be conveyed by the inter-machine table 52 and the rear surface tilting table 58. However, the feed velocities of multiple section bars cannot be similarly controlled when they are conveyed by the inter-machine table 52 and the rear surface tilting table 58 and a difference of velocities is caused between respective section bars having come off the multiple section bars straightening apparatus 51 and disposed in parallel with each other. Accordingly, it is very difficult to perform the n cut thereto within tolerance. To cope with this problem, the section bars having come off the multiple section bars straightening apparatus 51 are restricted by the inlet side presser roller 54 and the outlet side presser roller 57 so that the difference (delay) of velocities is not caused between the respective section bars disposed in parallel with each other.
As described above, means for feeding multiple section bars while restricting them are required upstream and downstream of the traveling cutting machine 55 to accurately cut them to the final cut (n).
In contrast, in order to prevent the bending of a section bar when it is cut while being restricted, the leading end of the section bar must be moved in the same direction as that in which a blade moves when it is cut. For this purpose, the rear surface tilting table 58 is installed.
FIG. 37 shows a specific example of the inline straightening/traveling cutting system for explaining a system employed in a company A. In FIG. 37, the portions having the same functions as those of FIG. 36 are denoted by the same numerals. Arrangements characteristic to the system will be specifically described based on FIG. 37.
First, a traveling cutting machine 55 will be described. The traveling cutting machine 55 employed by the company A is called a crank type shear. The crank type shear has a pair of crank shafts disposed above and below a pass line of a product. Crank arms are rotatably engaged with the crank shafts. The crank arms are formed to key shapes which are opposite to each other and execute operations at the upper end and the lower ends thereof. Then, an end of the key-shaped crank arm has a blade holder formed thereat on which a blade is mounted and the other end thereof is journaled by an arm which is swingable in a fan-shape.
The pair of crank shafts are rotated by a drive unit through gears. The rotation of the crank shafts causes the blade holders of the crank arms engaged therewith to make up/down symmetric motions with respect to the pass line. Then, the blades are opened, closed and opened in the one cycle of the motions to thereby cut a product.
Note that the upper and lower blades employed by the traveling cutting machine 55 are open blades independently mounted on the blade holders of the pair of crank arms and perform traveling and opening/closing motions (rising and falling motions) while the crank shafts rotate once.
FIG. 38 shows an example of the open blades. FIG. 38(a) shows open blades for angle steel, FIG. 38(b) shows open blades for channel steel, and FIG. 38(c) shows open blades for H steel. FIG. 39 is an A--A sectional view of FIG. 38. As can be seen from FIG. 39, the upper and lower blades are independently arranged and independently mounted on a cutting machine (shearing machine) so as to cross each other so that they can be overlapped. Note that the blades open and close (rise and fall) only in a vertical direction when viewed from the cut surface of a product.
FIG. 40 is a view showing another specific example of the inline straightening/traveling cutting system employed by a company B.
The traveling cutting machine 55 employed by the company B is a pendulum type shear.
The pendulum type shear comprises a crank shaft drive unit for opening and closing blades and a drive unit for rotating a crank shaft, which is different from the above crank shaft, for swinging a pendulum forward and backward for traveling cutting.
The blades are accommodated inside the pendulum and composed of independent upper and lower blades. The lower blade is fixed on the bottom base of the pendulum and the upper blade is mounted on a ram coupled with a blade opening/closing crank arm and opens and closes (rises and falls).
Note that the system of the company B does not use a presser roller and a product having comes off a straightening apparatus and to be subjected to "n cut" is transported by a roller (table) including a permanent magnet.
The conventional inline straightening/traveling cutting systems arranged as described above have various problems which will be described below as to classified items.
1. Problem as to the Traveling Cutting Machine
(1) Squareness of Cut Surface
In the conventional crank type shear employed by the company A, cutting is performed while the crank arms make elliptic motions. Whereas, in the pendulum type shear employed by the company B, cutting is performed while the pendulum is swung. Accordingly, in both the shears, a cutting angle is not constant in the lengthwise direction of a product, and cutting begins at "90.degree.-.alpha..degree. (or "90.degree.+.alpha..degree.) and finishes at 90.degree.. Therefore, the angle of the cut surface of the product cannot be made to 90.degree. geometrically. That is, in the crank type shear employed by the company A, the cut surface is made to a concave/convex shape as shown in FIG. 42, whereas to a convex shape as shown in FIG. 43 in the pendulum type shear employed by the company B.
Such a cut surface is never accepted in the markets of the countries where quality control is severely executed.
(2) Deformation of Cut Surface
Both the crank type shear and the pendulum type shear are an up-and-down-directional guillotine shear using the open blades as shown in FIG. 38, and the blades (upper blade and/or lower blade) move vertically with respect to a product regardless of the shape thereof, when viewed from the traveling direction of the product.
At the time, in the angle steel shown in FIG. 38(a), since the blades has an angle of 45.degree. with respect to a product while they move vertically, the product is cut in a minimum sheet thickness from the start of cutting to the finish thereof. As a result, the cut surface of the angle steel is not deformed and thus the crank type shear and the pendulum type shear are ordinarily used in Japan.
However, in the channel steel, H-steel and the like shown in FIG. 38(b) and FIG. 38(c), and the like, when the blade is moved vertically, a flat web portion is not deformed because it is thin. However, since flange portions, which are formed vertically with respect to the web, are cut in a height direction which is several times as long as the thickness thereof, they are buckled between the point thereof at which cutting is started and the point thereof at which the cutting is finished, whereby character-S deformation is caused thereto by the combination of the concave shape and the concave shape of a cut surface as shown in FIG. 43.
2. Problem Second Aspect to Presser Roller
In the system of pressing section bars against the inter-machine table or the rear surface table by a presser roller employed by a company P or in the system of restricting section bars by a magnet roller employed by a company D, since a plurality of rows of section bars cannot be tightly clamped, there arises a problem that the section bars are unevenly clamped by the dislocation of loosely clamped section bars.
This point will be described in more detail. In the presser roller system, it is arranged as if it was an upper-and-lower-confronting type pinch rollers as shown in FIG. 44. However, since a flat table roller 58a (the roller of the rear surface tilting roller), which transports all the products, also acts as a lower pinch roller, the surface of the table roller 58a is unevenly worn. Further, even if products are clamped, they are in point contact with the table roller 58a as shown by a and b in FIG. 44 due to the simultaneous occurrence of the bad conditions of product shapes and size errors, and intervals shown by c, d and e surrounded by circles in FIG. 44 are generated between the products and the presser roller 57.
Further, in the magnet roller, products are dislocated by the unstable restricting force of a magnet, in addition to the wear of the roller.
A method of shearing a section in a short time by using a fixed blade and a moving blade each provided with a caliber according to the cross-sectional shape of the section and moving the moving blade obliquely downward with respect to the section is disclosed in Japanese Unexamined Patent Publication No. 2-262908, Japanese Patent No. 2616365 and Japanese Unexamined Patent Publication No. 9-136213. In this case, the occurrence of sagging and burring to a cut surface can be prevented and even if they occur, they can be restricted within an allowable range by properly setting a sharing clearance between the fixed blade and the moving blade. However, the clearances between the calibers of the shearing blades and the section (hereinafter, referred to as clearances in the calibers) are, even if they are set to intervals which are contemplated proper, greatly affected by the dimensional tolerance of the section, the curving and bending thereof, the material and wear of the shearing blades, and the like, whereby the shape of the cut surface is often deformed as shown in FIG. 51. FIG. 51 shows modifications of the shape of the cut surface exemplified by channels steels, wherein (a) shows a deformation in which .theta.1&gt;90.degree.&gt;.theta.2 and .theta.1 and .theta.2 are not made to right angles, where the angle between one of flange surfaces and a web surface is shown by .theta.1 and the angle between the other of the flange surfaces and the web surface is shown by .theta.2, whereas (b) shows a case in which the corner portion of a web is sagged and the web is swelled.
These modifications of the cut surface are liable to be particularly caused in a hot-rolled section product in comparison with a cold-rolled section. A reason of it that the sizes and thicknesses of the leading end and the tail end of the hot-rolled section are somewhat increased as compared with those of the intermediate portion thereof. Thus, the size of the caliber must be increased to permit the hot-rolled section to pass therethrough and accordingly the clearance in caliber used in the hot-rolled section is made larger than that used in the cold-rolled section.
Japanese Patent No. 2616365 and Japanese Unexamined Patent Publication No. 9-136213 of the above publications do not take the problem of the clearance in caliber into consideration at all except the Japanese Unexamined Patent Publication No. 2-262908 in which a plurality of divided segment-shaped blades are adjustably disposed in the vicinity of the caliber of a moving blade holder.
However, a cutting method using the divided blades is effective only to a section having an excellent dimensional accuracy over the entire length thereof such as a cold-rolled section and is not applicable to a hot-rolled section because there is a danger of faulty cutting because a large clearance in caliber still exists. Further, the adjustment of the divided blades is time-consuming and troublesome because it is performed on the precondition that the size of a section is measured. Therefore, many problem are caused thereby also in cost. Further, since there are many section bars having a different flange thickness and a different web thickness even if they have the same size, it is actually very difficult and troublesome to set and adjust the clearance in caliber.
Further, the cutting methods disclosed in Japanese Unexamined Patent Publication No. 2-262908, Japanese Patent No. 2616365 and Japanese Unexamined Patent Publication No. 9-136213 relate to the cutting of a single section and do not relate to a multiple section bars cutting method for cutting a plurality of section bars at the same time.
Further, many modern section rolling equipment employ an inline section bar straightening/cutting system. In this case, a plurality of section bars are corrected and cut at the same time and the cut system of the equipment is roughly classified into a stop cutting type and a traveling cutting type. However, any of the types is not an obliquely cutting system for cutting section bars by obliquely moving a moving blade with respect to the section bars and is a vertical cutting system for cutting the section bars by moving the moving blade in a vertical direction. The following cut systems are employed to section bars having at least two surfaces meeting at right angles such as channel steel, H-steel, I-steel, rail and the like.
(1) Stop Cutting System
This is a punching system by means of a cutting machine called a punch cut or a double cut. However, a yield is bad in this system because chips of about 40 mm wide are produced. Further, there is a problem that the quality of a cut surface is not so good.
(2) Traveling Cutting Type
This is a traveling cutting system using a flying shear such as a pendulum shear, a rotary shear and the like. However, since a cutting angle between a blade and a section is not 90.degree. and the cutting angle is dispersed a few degrees in this system, there is a problem that a cut surface cannot be finished at right angles and post processing such as recut and the like must be performed.
It is conceived that an oblique cutting system using a fixed blade and a moving blade each having calibers is superior to the punching system and the cutting system using the flying shear in the quality of cut surface and efficiency. However, when this system is employed to cut multiple section bars, if respective moving blades move in parallel oblique directions as ordinarily conceived, the horizontal component of shear reaction is accumulated. As a result, the quality of a cut surface is deteriorated because backlash is made between shear blades.